INTERNAL ORGANS. H 



brane called mesentery^ which not only serves 

 this purpose, but affords also a bed for the 

 lacteals^ or those small vessels by which the 

 nutritious parts of the food are conveyed to the 

 heart, to be converted into blorr 1. Before we 

 proceed to a particular description of these 

 vessels, it will be necessary to explain the pro- 

 cess of nutrition. 



When food is taken into the mouth, it is 

 broken down by the teeth, and so mixed with 

 saliva, as to be in a proper state for entering 

 the stomach; it is then, by the. ur.ited action 

 of the toncfue and muscles of the throat, forced 

 into the oesophagus, u hence it passes into the 

 stomach. In this organ it undergoes a consi- 

 derable alteration ; for here Nature has pro- 

 vided a curious liquid called gastric juice. 

 which has the property of dissolving every 

 thino- that is taken into the stomach, and of 

 converting it into a soft pulpy mass, of a 

 uniform and homogeneous appearance. When 

 the food has been thus altered, "^the mass is 

 forced by a contraction of the stomach into the 

 duodenum, or first part of the intestinal canal ; 

 this mass, however, does not consist wholly of 

 nutritive parts, or such as are fit for the for- 

 mation of blood; and another operation is ne- 



